An aircraft uses an enhanced vision system (EVS) to provide imagery to an aircraft crew. The imagery can include an airport terminal area and runway environment when meteorological conditions prevent a clear natural view of the external surroundings of the aircraft through the windscreen. For example, the EVS may overlay an image of an airport terminal area and runway environment over the pilot's natural unaided view of the external surroundings of the aircraft through the aircraft's cockpit windscreen. Such imagery can improve the situational awareness of the flight crew during instrument approach procedures in low visibility conditions such as fog. That same enhanced vision system can be used as an FAA-certified enhanced flight vision systems (EFVS) which can allow pilots landing under instrument flight rules to operate below certain specified altitudes during instrument approaches even when the airport environment is not visible. For example, under Title 14 of the Code of Federal Regulations, part 91, a pilot may not descend below decision altitude (DA) or minimum descent altitude (MDA) to 100 feet above the touchdown zone elevation (TDZE) from a straight-in instrument approach procedure (IAP), other than Category II or Category III, unless the pilot can see certain required visual references. Such visual references include, for example, the approach lighting system, the threshold lighting system, and the runway edge lighting system. The pilot may, however, use an EFVS to identify the required visual references in low visibility conditions where the pilot's natural unaided vision is unable to identify these visual references. Accordingly, the use of an EFVS may minimize losses due to the inability of the pilot to land the plane and deliver cargo and/or passengers on time in low visibility conditions.
EVS imagery is typically presented to the pilot flying (PF) on a head up display (HUD). The HUD is typically a transparent display device that allows the PF to view EVS imagery while looking at the external surroundings of the aircraft through the cockpit windscreen. As long as visibility conditions outside of the aircraft permit the PF to see the external surroundings of the aircraft through the cockpit windscreen, the PF can verify that the EVS is functioning properly such that the imagery on the HUD is in alignment with the PF's view of the external surroundings of the aircraft.
EVS imagery is sometimes also presented to the pilot monitoring (PM) on a head down display (HDD). For example, in some countries, the system must present the EVS imagery to the PM for confirmation that the EVS information is a reliable and accurate indicator of the required visual references. The PM may also use the EVS imagery to determine whether the PF is taking appropriate action during approach and landing procedures. The HDD is typically a non-transparent display device mounted adjacent to or within a console or instrument panel of the aircraft.
An EVS typically uses either a passive or active sensing system to acquire data used to generate imagery of the airport terminal area and runway environment. A typical passive sensor, such as a forward looking infrared (FLIR) camera or visible light spectrum camera, receives electromagnetic energy from the environment and outputs data that may be used by the system to generate video images from the point of view of the camera. The camera is installed in an appropriate position, such as in the nose of an aircraft, so that the PF may be presented with an appropriately scaled and positioned video image on the HUD having nearly the same point of view as the PF when viewing the external surroundings of the aircraft through the HUD. However, while passive sensors provide higher quality video imagery, they may be unable to identify required visual references in certain low visibility conditions such as heavy fog.
Active sensing systems, such as millimeter wavelength (MMW) radar systems (e.g., 94 GHz), transmit electromagnetic energy into the environment and then receive return electromagnetic energy reflected from the environment. The active sensing system is typically installed in an appropriate position, such as in the nose of an aircraft. Active sensing systems are expensive and require space on-board the aircraft that is required for other types of equipment. In addition, MMW radar systems require expensive radome technology.
Additionally, both passive FLIR cameras and active millimeter wavelength radar systems may have limited range in certain low visibility conditions such as heavy fog.
Thus, there is a need for real time or near real time sensing systems for and methods of providing enhanced vision at longer ranges and in inclement weather. Further, there is a need for real time or near real time sensing systems for and methods of providing enhanced vision imagery that is less expensive and does not require additional space on the aircraft. There is also a need for display systems for and methods of providing images of the external scene topography using radar data from a weather radar system. There is still a further need for systems for and methods of providing images of the runway environment derived from weather radar data where such images enable operation below certain specified altitudes during instrument approaches. Further still, there is a need for systems and methods that achieve higher resolution imaging using X-band and C-band radar data.
It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments which fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.